The present invention relates generally to the field of transducer communication through walls, and in particular to simultaneous bi-directional communication between a single pair of piezoelectric transducers.
A transducer is a device that converts one form of energy to another. Transducers may be used, among other functions, to transmit and receive data and power across a solid barrier without requiring any holes in the barrier. Conceptually, this can be done by a first transducer on one side of a barrier turning electrical energy into mechanical energy, the mechanical energy traveling across the barrier, and being received by a second transducer on the other side of the wall which converts some portion of the mechanical energy back into electrical energy. This ability is particularly useful for transmitting energy and data through barriers like ship and submarine hulls, pressure vessel tanks, and other walls separating extreme environments where it is undesirable to create physical openings for wires.
Ideally, transducer devices should be attached directly to the communications barrier, though many arrangements are possible. It is generally desirable to have a smooth, uninterrupted, uniform barrier between coupled transducers.
Published patent application US2010/0027379, published Feb. 4, 2010 and incorporated herein by reference, discloses an ULTRASONIC THROUGH-WALL COMMUNICATION (UTWC) SYSTEM for communicating digital information through a barrier in the form of a thick metal wall, using ultrasonic techniques so that no through-holes are needed in the barrier. Using this system, signals can be transmitted through the barrier. For example, sensor signals that monitor conditions on one side of the barrier can be transmitted to the other side of the barrier. The barrier may be the wall of a pressure vessel and the conditions to be monitored may be those of a hostile, high temperature and high pressure, gaseous or liquid environment in the pressure vessel.
U.S. Pat. No. 7,902,943 to Sherrit et al. discloses a WIRELESS ACOUSTIC-ELECTRIC FEED-THROUGH FOR POWER AND SIGNAL TRANSMISSION including a first piezoelectric transducer to generate acoustic energy in response to electrical energy from a source, and a second piezoelectric transducer to convert the received acoustic energy to electrical energy to be used by a load.
U.S. Pat. No. 7,894,306 to Martin et al. for an APPARATUS AND METHOD FOR DATA TRANSFER THROUGH A SUBSTRATE discloses transferring data through a submarine hull or other solid boundary using high frequency acoustic signals to avoid penetration of the hull or boundary.
U.S. Pat. No. 5,982,297 to Welle discloses an ultrasonic data communication system including first and second transducers coupled together through a coupling medium for communicating input and output undulating pressure waves between the transducers for the transfer of input and output data between an external controller and an embedded sensory and actuating unit. An internal processor powers the second embedded transducer to generate ultrasonic waves into the medium that are modulated to send the data from the embedded sensor so that considerable energy is needed for the embedded circuits.
Also see U.S. Pat. Nos. 6,625,084; 6,639,872; 7,514,844; 7,525,398 and 7,586,392 for other approaches to the transmission of data or power through a barrier using ultrasound.
A more comprehensive approach to wireless data and power transmission through a barrier is taught by R. Primerano in “High Bit-rate Digital Communication through Metal Channels,” PhD dissertation, Drexel University, July 2010, hereafter referred to as Primerano. Without conceding that Primerano is prior art to the invention disclosed in the present application, Primerano is interesting because it teaches Orthogonal Frequency-Division Multiplexing or OFDM modulation with a cyclic prefix to send data at a high rate through a metal wall using ultrasound. The use of OFDM compensates for signal loss due to echos caused by boundaries or due to other incongruities across the channel. Primerano does not, however, teach a system that simultaneously delivers power in one direction while data is transmitted in one or both directions.
Using transducers to send vibrational signals through a wall presents special challenges. Unlike more traditional arrangements, separate channels, such as separate wires, cannot easily be provided to segregate communication between different components and in different directions between the same components, or even to segregate power transmission from signal transmission. All communications—in both directions—must be passed through the same solid wall.
Prior-art arrangements have provided a plurality of transducer pairs aligned across a single wall to create multiple channels for communication of signals and transfer of power. Different transducer pairs can be used and designed for different purposes. Multiple transducer pairs can, however, add complexity and expense, will typically require greater surface area for mounting, and may be difficult to align on opposite sides of the communication wall. Multiple transducers can also interfere with each other since they are still passing vibrations across the same substrate. As a result, arrangements including multiple pairs of transducers are not desirable for all applications.
Using only a single pair of transducers presents other difficulties. The same section of wall and same pair of transducers must be used both to send and to receive power and to send and receive information. Further, it will often be desirable to send energy and/or information through the wall in both directions at once. Vibrations simultaneously sent through a section wall in opposite directions will often cancel and/or interfere with each other.
As a result, there is a need for improved methods and arrangements to simultaneously send accurate communications in both directions, through a single section of wall, using only a single pair of aligned transducers. It is particularly desirable to provide a system able to correct for interaction between a received signal and a signal sent simultaneously in the opposite direction through the same carrier.